NEW YORK -- A federal grand jury indicted the former chairmen of Sotheby's Holdings Inc. and Christie's International PLC on charges that they masterminded an international scheme to fix commissions levied on clients of the world's two largest auction houses.

The indictment, filed in U.S. District Court in Manhattan, accuses real-estate mogul A. Alfred Taubman, the controlling shareholder of Sotheby's, and Sir Anthony J. Tennant of colluding on how the auction houses dealt with art sellers from 1993 through 1999, including...